DESCRIPTION (Adapted from applicant's description): Less than 10% of transferred human IVF embryos establish a pregnancy. In other species, the losses are not as high, but are appreciable. Some in vitro embryo culture systems are associated abnormal phenotypes including large birth weights and often embryonic, fetal or newborn death. Embryos that result in abnormally large offspring display a normal morphology when transferred. This highlights the importance of evaluating culture influences on genetic characteristics in addition to morphological parameters. Culture environments must not only sustain development and morphology, but also maintain normal patterns of gene expression. The overall goal of this proposal is to develop safe, effective, and efficient methods for mammalian embryo culture. The specific aims will evaluate the quality of bovine embryos produced by a variety of in vitro culture methods by determining the influence of culture on insulin-like growth factor (IGF) and interferon tau (bTP1) gene expression. These molecules are important targets for examining the unusual growth rates of cultured bovine embryos as altered levels of these genes are likely to reflect changes in the developmental program of early embryogenesis. The experiments will examine the following specific aims: 1: To determine the effects of culture on the expression of mRNAs encoding IGFI, IGFII and their receptors. 2: To determine the effect of culture on the cellular distribution of IGF polypeptides. 3: To determine the effects of culture on expression and secretion of bTP1. 4: To determine the influence of culture on IGF secretion. 5: To determine the effect of culture on bovine embryo development. 6: To isolate and characterize culture sensitive differentially expressed transcripts (mRNAs) in early embryos using differential display techniques (RT-DDPLR).